1. Field of the Invention
This invention relates to a combustion chamber to burn gas, and more particularly to a pressure balance housing that mounts to the combustion chamber for use with a pilot or a sensor.
2. Description of Prior Art
A wide variety of apparatuses are currently used to burn gases. A common application involves burning fuel gases in main burners to inject heat into some process. For example, electrical power producers may burn natural gas to generate steam to drive electric generators. Refinery operators may use the heat in catalytic cracking units (xe2x80x9ccat-crackersxe2x80x9d) to break up long hydrocarbon chains, or in distillation units to separate the various hydrocarbon constituents in crude oil. Refiners may also want to dispose of gaseous waste by-products by incinerating them. Manufacturers often use heat to prepare their raw or partially treated materials for the next step in their manufacturing process.
In many applications a burner is supplied with a fuel to cause a flame. The gasses to be burned are delivered to the combustion chamber for burning by the burner. A pilot is generally used to light the burner. The burner is typically located in an enclosure having a vent, such as a smokestack, to vent byproducts from the burning by creating negative pressure in the chamber. A blower in the vent may assist in creating the negative pressure. A recirculation conduit may return some of the byproducts for further burning. Various factors, such as the wind flowing across the upper end of the stack, the blower, the extent of recirculation, and natural convection can produce a variable low pressure region in the chamber. That low pressure can either directly or indirectly cause the burner and the pilot to go out. This is very unsafe because fuel may be supplied to the burner, or waste gases routed to the burner for disposal, but the gases do not ignite because of the extinguished pilot. That leads to an unsafe accumulation of fuel, or the failure to safely dispose of waste gases.
Also, in many cases it is desired to measure characteristics of the gas in the combustion chamber, such as its constituents, temperature, pressure, the presence of flame etc. This is not easily performed because of the high temperatures within the chamber.
The present invention uses a pressure balance unit mounted to the chamber. The unit includes a housing inner portion mounted to the combustion chamber, the housing inner portion having an inner end with an opening communicating with the interior of the combustion chamber. A housing outer portion is on an outer end of the housing inner portion. An annular intake is located between the housing inner and outer portions for drawing ambient air into the housing inner and outer portions. The intake and the opening in the housing inner portion have flow areas sized so as to balance pressure in the housing outer portion with pressure in the chamber.
A tube extends through the housing outer portion and has an open inner end in the combustion chamber. The tube has an orifice adjacent its inner end within the housing outer portion. A pilot may be incorporated with the tube, so that gas flows from the intake, through the orifice and into the combustion chamber, where it is ignited. The pressure balancing unit causes the pressure in the housing outer portion to fluctuate up and down in unison with pressure fluctuations in the chamber. This results in the air flow into the tube increasing and decreasing in response so reduce the chances for the pilot to go out.
Further, a sensor may be mounted in the tube outward of the orifice. In this case, the intake is adjusted so that the pressure in the housing outer portion is slightly less than the pressure in the chamber. This causes gas in the chamber to flow into the tube and out the orifice into the housing outer portion. The sensor monitors characteristics of the gas.